do not add newlines to direct process.stdout/stderr writes, fixes #319 under posix
Merge #688 r=@tcr: Do not add newlines to direct process.stdout/stderr writes

Fixes #319 for "PC" use cases. Depends on https://github.com/tessel/cli/pull/166 — otherwise as it sits now, the CLI will silently drop the new "raw" messages by default.